Extendable panel fasteners have a variety of applications including assembly to a printed circuit board which most recently utilizes surface mount technology (SMT). Retractable panel fasteners allow a considerable float of the screw relative to the retainer portion to compensate for misalignment, however this flexibility presents a difficulty in the pick-and-place aspect of the circuit board surface mount process. In the pick-and-place process, the fastener is held (typically pneumatically) by the topmost portion of the screw and then placed onto the printed circuit board (PCB). The above-mentioned floating nature of the integrated cap/screw portion with regard to the retainer result in the retainer not always being centered under the screw and hence, since placement is controlled by the position of the screw, the retainer might not find its intended mounting hole in the PCB.
A solution for this problem known in the art is to provide a panel fastener which has means to hold itself in its compressed, screw-extended position so that a firm and stable centered assembly is provided to the pick-and-place surface mount assembly process. One example of such a device is described in U.S. Pat. No. 8,113,755 issued to Wang. In accordance with this document, a stop ring such as an o-ring or a nut is placed about the end of the screw and positioned to abut the end of the retainer when the screw is in its extended position. Once the panel fastener has been assembled to the PCB, the ring or nut is removed. While this solution solves the pick-and-place problem of a floating SMT panel fastener, it is less than ideal since it requires the additional step of removal of the nut and ring and the attendant problem of disposing of the scrap waste.